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Commanded by Major General Samuel P. Heintzelman
Defences North of the Potomac Lieutenant Colonel Joseph A. Haskin  
First Brigade Colonel J. M. Warner  
1st Maine Heavy Artillery, Co. M    
2nd Pennsylvania Heavy Artillery    
1st Vermont Heavy Artillery    
Second Brigade Colonel Lewis O. Morris  
16th Indiana Battery    
1st Maine Heavy Artillery    
7th New York Heavy Artillery Colonel Lewis O. Morris  
9th New York Heavy Artillery    
9th New York Independent Battery    
117th New York Infantry, 2nd Battalion   to Dept. VA., 7 Corps, 2 Div., 1 Brig.
Third Brigade Colonel William R. Pease (to 4/14)
Colonel A. Piper
 
5th New York Heavy Artillery,
Companies A, I, K, L & M
   
10th New York Heavy Artillery    
117th New York Infantry, 1st Battalion   to Dept. VA., 7 Corps, 2 Div., 1 Brig.
Defences South of the Potomac Brigadier General Robert O. Tyler (4/15- 4/26)
Colonel T. R. Tannatt
 
First Brigade Colonel T. R. Tannatt organized 4/15 
1st Massachusetts Heavy Artillery   from Art. Alexandria (below)
2nd New York Heavy Artillery   from Art. Alexandria (below)
3rd New York Heavy Artillery Battalion   from Art. Alexandria (below)
4th New York Heavy Artillery   from Abercrombie’s Div. (below)
1st Wisconsin Heavy Artillery, Bat. A   from Art. Alexandria (below)
Second Brigade Colonel G. D. Wells organized 4/15 
1st Connecticut Heavy Artillery Colonel Henry L. Abbott from Art. Alexandria (below)
19th Connecticut Infantry Regiment Colonel Leverette Wessells from Art. Alexandria (below)
34th Massachusetts Infantry Regiment   from Art. Alexandria (below)
16th West Virginia Infantry Regiment   from Abercrombie’s Div., 2 Brig. (below)
Abercrombie’s Division Brigadier General J. J. Abercrombie  
First Brigade Colonel Francis Fessenden  from Casey’s Div. 1 Brig. (below)
25th Maine Infantry Regiment    
27th Maine Infantry Regiment    
Second Brigade (until 4/17) Colonel B. Porter to Dept. Virginia 4/17
22nd Connecticut Infantry Regiment    
40th Massachusetts Infantry Regiment    
141st New York Infantry Regiment    
16th West Virginia Infantry Regiment    
Second Brigade (after 4/17) Brigadier General George J. Stannard from Casey’s Div. 2nd. Brig.
12th Vermont Infantry Regiment    
13th Vermont Infantry Regiment    
14th Vermont Infantry Regiment    
15th Vermont Infantry Regiment    
16th Vermont Infantry Regiment    
Third Brigade (until 4/17) Colonel William Gurney to Dept. Virginia 4/17
127th New York Infantry Regiment    
142nd New York Infantry Regiment    
143rd New York Infantry Regiment    
144th New York Infantry Regiment    
Third Brigade (after 4/17) Brigadier General Alexander Hays (to 4/26)
Colonel George L. Willard
from Casey’s Div. 3rd Brig.
39th New York Infantry Regiment    
111th New York Infantry Regiment    
125th New York Infantry Regiment    
126th New York Infantry Regiment    
Artillery    
9th Massachusetts Battery    
17th New York Independent Battery    
2nd Connecticut Independent Battery   from Casey’s Div. Artilery (below)
11th Massachusets Independent Battery   from Casey’s Div. Artilery (below)
4th New York Heavy Artillery   to 1 Brig. Derussy’s Div. (above)
1st Rhode Island Light Artillery, Battery H   from Casey’s Div. Artilery (below)
Keystone (Pennsylvania) Battery   from Casey’s Div. Artilery (below)
Casey’s Division Major General Silas Casey  
First Brigade Colonel Francis Fessenden to 1 Brig. Abercrombie’s Division (above)
25th Maine Infantry Regiment    
27th Maine Infantry Regiment    
Second Brigade Brigadier General George J. Stannard to 2 Brig.  Abercrombie’s Division (above)
12th Vermont Infantry Regiment    
13th Vermont Infantry Regiment    
14th Vermont Infantry Regiment    
15th Vermont Infantry Regiment    
16th Vermont Infantry Regiment    
Third Brigade Brigadier General Alexander Hays to 3 Brig. Abercrombie’s Division (above)
39th New York Infantry Regiment    
111th New York Infantry Regiment    
125th New York Infantry Regiment    
126th New York Infantry Regiment    
Artillery    
9th Massachusetts Battery    
17th New York Independent Battery    
2nd Connecticut Independent Battery    
11th Massachusets Independent Battery    
4th New York Heavy Artillery    
1st Rhode Island Light Artillery, Battery H    
Keystone (Pennsylvania) Battery    
Pennsylvania Reserves Division Colonel Horatio G. Sickel  
First Brigade Colonel William Sinclair  
1st Pennsylvania Reserves Regiment    
2nd Pennsylvania Reserves Regiment    
6th Pennsylvania Reserves Regiment    
13th Pennsylvania Reserves Regiment    
Second Brigade Colonel H. C. Bollinger to 4/12
Colonel H. G. Sickel  (to 4/15)
Colonel H. C. Bollinger
to District of Alexandria (below)
3rd Pennsylvania Reserves Regiment    
4th Pennsylvania Reserves Regiment    
7th Pennsylvania Reserves Regiment    
8th Pennsylvania Reserves Regiment    
Third Brigade Colonel J. W. Fisher  
5th Pennsylvania Reserves Regiment    
9th Pennsylvania Reserves Regiment    
10th Pennsylvania Reserves Regiment    
11th Pennsylvania Reserves Regiment    
12th Pennsylvania Reserves Regiment    
Cavalry Division Major General Julius Stahel  
First Brigade Brigadier General Joseph T. Copeland  
5th Michigan Cavalry Regiment    
6th Michigan Cavalry Regiment    
7th Michigan Cavalry Regiment    
Second Brigade Colonel R. Butler Price  
1st Michigan Cavalry Regiment    
1st Ohio Cavalry Cos. A&C    
2nd Pennsylvania Cavalry Regiment    
1st Vermont Cavalry Regiment    
Third Brigade Lieutenant Colonel R. Johnston (to 4/9)
Colonel O. DeForest
 
5th New York Cavalry Regiment    
18th Pennsylvania Cavalry Regiment    
1st West Virginia Cavalry Regiment    
Jewett’s Independent Brigade Colonel A. B. Jewett  
23rd Maine Infantry Regiment Colonel William W. Virgin  
39th Massachusetts Infantry Regiment Colonel P. Stearns Davis  
14th New Hampshire Infantry Regiment Colonel Robert Wilson  
10th Vermont Infantry Regiment Colonel Albert B. Jewett  
11th New York Cavalry, Cos. E, F & I    
10th Massachusetts Independent Battery    
District of Washington Brigadier General J. H. Martindale  
2nd District of Columbia Infantry Regiment Colonel Charles M. Alexander  
10th New Jersey Infantry Regiment Colonel William R. Murphy to 7th Corps, 1st Div., 3rd Brig.
118th New York Infantry Regiment   to 7th Corps, 1st Div., Reserve Brig.
152nd New York Infantry Regiment   to 7th Corps, 1st Div., 1st Brig.
169th New York Infantry Regiment   to 7th Corps, 1st Div., 2nd Brig.
27th Pennsylvania Infantry, Co. F    
150th Pennsylvania Infantry, Co. K    
157th Pennsylvania Infantry (4 cos.)    
District of Alexandria Brigadier General John P. Slough  
1st District of Columbia Infantry Regiment    
26th Michigan Infantry Regiment   to 1 Brig., 1 Div., 7 Corps, Dept. VA
153rd New York Infantry Regiment    
Pennsylvania Independent Battery H   from Camp Berry (below)
11th Rhode Island Infantry Regiment Colonel George E. Church to 1 Brig., 1 Div., 7 Corps, Dept. VA
Artillery, Distict of Alexandria Brigadier General Robert O. Tyler  
1st Connecticut Heavy Artillery Colonel Henry L. Abbott to Defences S. of the Potomac, 2 Brig
19th Connecticut Infantry (Hv. Artillery) Colonel Leverette Wessells to Defences S. of the Potomac, 2 Brig
Artillery Brigade South of the Potomac Colonel M. Cogswell  
1st Massachusetts Heavy Artillery    
34th Massachusetts Infantry Regiment Colonel George D. Wells  
2nd New York Heavy Artillery   to Defences South of  Potomac, 1 Brig.
3rd New York Heavy Artillery Battalion    
1st Wisconsin Heavy Artillery    
Light Artillery Camp Camp Barry Brigadier General William F. Barry  
1st Delaware Battery   to Dept. Virginia, 7 Corps Art. 4/18
9th Michigan Battery   to Cav. Div. (above)
10th Michigan Battery    
1st New York Artillery, Battery A    
4th New York Heavy Artillery   to Defences S. Potomac 1 Brig. (above)
12th New York Independent Battery    
16th New York Independent Battery   to Dept. Virginia, Suffolk
19th New York Independent Battery   to Dept. Virginia, Suffolk
27th New York Independent Battery    
1st West Virginia Artillery, Battery A